1. Field of the Invention
The invention relates to power generation, energy-transfer and usage in space by a mobile Solar Sail Power Station spacecraft, which utilizes Roller-Reefing as fuelless means of station keeping, steering, attitude control and pointing, combined with enhanced energy production through additional usage of the solar sail foils as large solar cell arrays.
2. Description of the Related Art
The related US-patent U.S. Pat. No. 6,194,790 discusses a solar sail, made or covered with thin film solar cells which is guided towards Sun with the help of thrusters to produce electric power, while a power line connection feeds a nearby satellite.
A weak point of this concept is, that the power sail needs fuel for station keeping and attitude control to produce electric energy and that this craft is thought for rather immobile applications.
The thrusters are just thought to keep the sail pointed toward Sun, while the solar radiation pressure pushes the craft away of it.
Space based solar power satellites (SBPS) can only produce electricity, if they are pointing to a large degree towards Sun with large reflecting mirror or with solar-cell arrays. While doing this, they will be pushed away from the Sun by SRP-forces (up to about ≈4.5 N per km2 of foil area in Earth orbit, if the foil is not reflecting).
Power satellites have to provide station keeping, attitude control and steering while pointing towards Sun (with mirrors or solar cell arrays for the power collecting unit) and pointing towards Earth (for the transmitting antenna or laser unit) and should preferably stay in GEO while the solar radiation pressure is pushing it.
For years of operation of a large power satellite, tons of fuel would have to be delivered to GEO if thrusters are used for station keeping and attitude control.—Just to keep a large SBPS in a stable orbit and to provide pointing and steering while the spacecraft is orbiting Earth and has to change continually it's pointing direction towards Sun to stay in the GEO-orbit.
Solar Sails on the other hand are thought for fuel-less space transportation, though most designs lack the capacity to handle payload AND daughter units and do not or only in a modest scope produce solar power.
Ikaros, the Japanese space probe, the first solar sail spacecraft, which is free flying and accelerating by solar radiation pressure (SRP) in space now, has already some solar cells integrated on the solar sail foils, but has no payload handling capacity and is because of it's spin stabilization (and the inherent inertia of such a large spinning plane) hard to steer.
Such a spinning craft would not be able, to point towards Sun and Earth at the same time.
The previous prior art solar-sail designs of the inventor do already feature a central payload and docking station for mother units and combine simple sail setting and reefing by “Roller-Reefing” and can use this technology also for steering, fuel-less station keeping and attitude control.
Roller-Reefing is also available for both, large space constructed solar sail spacecraft (see the inventor's German patent DE 10 2005 028 3780) and for direct launched craft without in space construction (see U.S.-patent U.S. Pat. No. 6,194,790).
There are already solar cells for power production integrated to the spacecraft structures, but only in modest scope. A possibility to use the full size of the large sail foils of the solar sail spacecraft for power production, was lacking until it has been proposed and published at and for the 2nd International Symposium on Solar Sailing in New York, (Jul. 20-22, 2010) by the inventor.